Components of certain equipment, such as that used in the petroleum and petrochemical industry, which includes the exploration, production, refining, manufacture, supply, transport, formulation or blending of petroleum, petrochemicals, or the direct compounds thereof, are often monitored to maintain reliable operation. However, such components can involve harsh conditions, such as high temperature, high pressure, and/or a corrosive environment, making it difficult or costly to obtain reliable measurements.
Detection of coking formation in a wash bed of a vacuum pipe still (VPS) distillation tower can allow operators to alter operating parameters to increase utilization of the bed and thus enhance operations. For example, detecting coking formation at an early stage and knowing its location within the wash bed in the VPS distillation tower can allow for mitigation strategies such as increasing the flow rate of wash oil to remove the coking.
Conventional techniques for detection of coking/fouling, and/or corresponding maldistribution resulting from such coking in such equipment as catalytic hydroprocessing reactors, can include monitoring temperature distribution to identify hotspots and infer flow distribution. Such techniques often rely on multiple thermocouples to monitor temperature distribution, e.g., inside fixed bed catalytic hydroprocessing reactors. However, the number of thermocouples used for hot-spot detection within a VPS wash bed or reactor catalyst bed can be limited by the space inside the bed and the cost of installation and maintenance. Thus, it can be difficult to provide adequate coverage inside the fixed bed space for sufficient hot spot detection. Likewise, flow conditions inferred from the limited point temperature measurements provided by thermocouples, constrained by the physical size of the thermocouples as well as the cost of installation and maintenance, can be inaccurate.
Other techniques to detect coking, and/or corresponding flow maldistribution, can include monitoring the delta pressure between the top and bottom of the wash bed. However, this technique is not without disadvantages, such as for vacuum tower wash beds, where the pressure drop is typically only on the order of a few mmHg in these wash beds when coking occurs. Thus, pressure measurement can be a highly unreliable indicator of coking. Similarly, temperature differentials between bulk temperatures have also been used to detect coking. However, this technique involves a gross measurement and thus not necessarily accurate.
Accordingly, there is a continued need for improved techniques for detecting coking/fouling growth and maldistribution in components of refinery equipment such as a wash bed of a VPS distillation tower.